In response to chronic metabolic acidosis, rat and dog kidneys extract more glutamine and produce more ammonia. Concomitant with this, lactate removal decreases so that overall renal oxidative decarboxylation does not seem to change. We feel that the adaptive ammoniagenesis during acidosis is tied in with these metabolic events, i.e. either augmented glutamine metabolism decreases lactate metabolism and/or the inhibition of lactate metabolism decreases glutamine metabolism. The purpose of our investigation is to prove that augmented renal ammoniagenesis seen in acidosis is secondary to alterations in oxidative metabolism and to define these events.